Activities for loops

Let’s use a ||loops:repeat|| loop to make a siren.

• From the ||input:INPUT|| Toolbox drawer, drag an ||input:on shake|| block onto the Workspace.
• From the ||loops:LOOPS|| Toolbox drawer, drag a ||loops:repeat|| loop onto the Workspace and place inside the ||input:on shake|| block.
• From the ||light:LIGHT|| Toolbox drawer, drag 2 ||light:show ring|| blocks onto the Workspace and place them inside the ||loops:repeat|| loop.
• Change the colors of the ||light:show ring|| block lights to flash blue and red like a siren.
• From the ||music:MUSIC|| Toolbox drawer, drag a ||music:play sound|| block onto the Workspace and place inside the ||input:one shake|| block, above the ||loops:repeat|| loop.
• In the ||music:play sound|| block, use the drop-down menu to change the sound to “siren”.

input.onGesture(Gesture.Shake, function () {
    music.siren.play()
    for (let i = 0; i < 4; i++) {
        light.showRing(
        "red red red red red red red red red red"
        )
        light.showRing(
        `green green green green green green green green green green`
        )
    }
})

Click the SHAKE button on the Simulator on the left, and you can preview the Circuit Playground Express’ behavior.

Finally, practice using ||loops:pause|| blocks. Place one after each ||light:show ring|| and change the duration of the pauses. Press SHAKE again in the Simulator, and you will see how different pause durations affect the siren you have made.

loops.pause(100)

A final reminder on loops – if you are using sensor data, like from the sound, light, accelerometer, etc. then you probably want those blocks inside a ||loops:forever|| loop because you want the Circuit Playground Express to be continuously checking whether it is being tilted, what the sound level is, etc. It’s possible you may only want to check sensor data on a specific input, like if a button is pressed, but usually you’ll need a ||loops:forever|| loop.